In an electronic component storing package (hereinafter, also referred to simply as a “package”) in which an electronic component such as a semiconductor component that generates heat is stored, a heat dissipating member with excellent thermal conductivity is used in a base member and the like. The heat dissipating member used in a base member and the like is required to have a good thermal conductivity and to have a coefficient of thermal expansion matching that of the electronic component. Also, the heat dissipating member is required to have properties such as high electrical conductivity. Since it is difficult for a single metal material to have all of these properties, a heat dissipating member that is made from a composite material in which a plurality of types of materials are combined has been used conventionally.
For example, Japanese Unexamined Patent Publication JP-A 2004-249589 discloses a heat dissipating member in which at least seven copper (Cu) plates 21 and molybdenum (Mo) plates 22 are stacked as shown in FIG. 7. This heat dissipating member 23 is produced by stacking the molybdenum layers and the copper layers so that the thickness of each single layer is 25% or less of the total plate thickness and then rolling the layers using a pressure-roller in a tensioned state. Furthermore, components such as a heat sink can be produced from the rolled composite material using a press-cutting machine or a press-punching machine.
Although not shown, Japanese Unexamined Patent Publication JP-A 3-218054 (1991) discloses, as an example of conventional heat dissipating members, a heat dissipating member that is made of a copper or copper alloy member, and any one of molybdenum, tungsten, and an alloy thereof that is securely attached to the copper or copper alloy member and whose thickness is 1/20 to ⅓ of that of the copper or copper alloy member.
However, in the above-described conventional heat dissipating members, the thermal conductivity is insufficient for recent electronic components that generate a large amount of heat in operation, and, thus, there is a problem in that the operation temperature of the electronic components may not be kept at the limit or lower.
Furthermore, there is also a problem in that it is difficult to provide good thermal conductivity and to control the coefficient of thermal expansion of the heat dissipating member at a desired value.